Abstract: We describe an experiment in which we test how the quality of collaboratively built IDEF0 and UML models is influenced by the collaboration process. Two collaborative modelling approaches were compared: a 'free-form' approach and an approach that singles out the concept elicitation phase by means of a specific 'generation' pattern. An error classification framework was used to compare the quality of the resulting models. We found that the semantic quality of UML models can be significantly improved by an explicitly separated generation task.